How does the presence of double bonds in rubber molecules influence their structure and reactivity?

(N/A) Natural rubber is a linear $cis$-polyisoprene in which the double bonds are present between $C_{2}$ and $C_{3}$ of the isoprene units as shown below:
$CH_2-C(CH_3)=CH-CH_2-CH_2-C(CH_3)=CH-CH_2$
Because of this $cis$-configuration,the chains do not fit together well,leading to weak intermolecular interactions between the various strands of isoprene. As a result,the strands in natural rubber are arranged randomly in a coiled structure. This allows the polymer to stretch,which gives it its characteristic elasticity.